There is need for a brief but comprehensive objective assessment tool to help clinicians evaluate relapse symptoms in patients with multiple sclerosis (MS) and their impact on daily functioning, as well as response to treatment. The 2-part Assessing Relapse in Multiple Sclerosis (ARMS) questionnaire was developed to achieve these aims. Part 1 consists of 7 questions that evaluate relapse symptoms, impact on activities of daily living (ADL), overall functioning, and response to treatment for previous relapses. Part 2 consists of 7 questions that evaluate treatment response in terms of symptom relief, functioning, and tolerability. The ARMS questionnaire has been evaluated in 103 patients with MS. The most commonly reported relapse symptoms were numbness/tingling (67%), fatigue (58%), and leg/foot weakness (55%). Over half of patients reported that ADL or overall functioning were affected very much (47%) or severely (11%) by relapses. Prescribed treatments for relapses included intravenous and/or oral corticosteroids (87%) and adrenocorticotropic hormone (13%). Nearly half of patients reported that their symptoms were very much (33%) or completely resolved (16%) following treatment. The most commonly reported adverse events were sleep disturbance (45%), mood changes (33%), weight gain (29%), and increased appetite (26%). Systematic assessment of relapses and response to relapse treatment may help clinicians to optimize outcomes for MS patients.